This invention relates to automotive hoists, and particularly to a portable auxiliary support mechanism that is installed between the service station floor and the hoist platform so that the platform remains in its elevated position if the hydraulic lifter system fails or malfunctions.
Automotive hoists are commonly used in service stations to support automobiles in elevated positions above the floor surface when it is desired to perform service work. Such hoists are usually elevated by pumping hydraulic fluid from a reservoir into a vertical cylinder. A vertical piston is raised from the cylinder to raise the hoist structure and automobile to an elevated position. The hoist is lowered toward the floor by releasing the hydraulic fluid from the cylinder back to the reservoir so that the weight of the hoist and load lowers the hoist.
As a safety feature, automotive hoists are very often equipped with auxiliary safety devices that automatically support the hoist in the elevated position if the hydraulic system should fail or malfunction. The safety devices are usually built into the hoist structure at the time of manufacture or installation.
U.S. Pat. No. 2,956,643 which was issued to J. H. Halstead on Oct. 18, 1960, discloses a safety device that includes an auxiliary piston telescopically fitted into a vertical cylinder that is sunk into the floor adjacent the main hoist cylinder. The upper end of the auxiliary piston is attached to the hoist platform to extend out of the vertical cylinder as the hoist is raised from the floor. A latching bar, pivotally carried by the auxiliary piston, drops under the influence of gravity to a position extending across the upper end of the auxiliary cylinder, thereby blocking the auxiliary piston from falling in its cylinder. The auxiliary piston--cylinder mechanism functions as a safety device preventing the hoist from inadvertently falling.
U.S. Pat. No. 3,833,091, issued to R. MacPherson on Sep. 3, 1974, discloses a safety device of the piston-cylinder type, wherein the auxiliary piston is held in its elevated position by two ball-shaped detents seated in convergent grooves at the upper end of the associated cylinder. The ball-shaped detents are wedged between the groove surfaces and the piston side surfaces to normally hold the auxiliary piston in its elevated position. By rotating the piston around its axis, it is possible to register two flat side surfaces of the piston with the ball detents, whereby the ball detents no longer act as wedge locking elements. The piston is thus freed to drop into the associated cylinder.
In the above-described patented arrangements, the auxiliary support mechanisms are built into the hoist structure when originally manufactured. The support mechanism has to be installed in the service station floor as part of the process of installing the hoist mechanism.
Many hoists have been built without auxiliary support mechanisms. The safety support mechanisms shown in the above-noted patents cannot be economically added to such hoists because of the difficulties involved in embedding the auxiliary cylinder in the floor. Considerable expense would be involved in drilling a vertical hole in the cement floor with sufficient precision to accurately locate the auxiliary piston.